The invention discloses a test and assessment method for a surrounding rock relaxation zone on the basis of the electromagnetic radiation principle, relating to the technology of test and assessment of the surrounding rock stress state or the relaxation zone (or a decompression zone) through test of electromagnetic radiation information in a surrounding rock drill hole. The observation method is as follows: a laneway or a tunnel zone to be tested is selected at first; drilling is performed according to the required direction; an electromagnetic radiating antenna of the drill hole is used for testing the electromagnetic radiation information on different positions in the drill hole; Ei is obtained after test is finished until all the observation points are tested. The assessment method is as follows: the assessment index adopts the mean value of the coal rock electromagnetic radiation intensity Ei, the mean value Eavg of the coal rock electromagnetic radiation intensity Ei of all the observation points is calculated; the test results Ei are displayed in an image; zones where the electromagnetic radiation intensity values of over two continuous observation points are larger than Eavg are assessed as high stress zones; the highest stress zone is a stress concentration zone; if a secondary-high stress zone exists, the secondary-high stress zone is an internal stress zone; the areafrom an orifice to the boundary of the stress concentration zone is a relaxation zone.